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Old 08-13-2006, 07:15 AM
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new383ci dyno hp is low

a friend of mine has this combo and the power he got wasn't WATS he thought
265.2 PK 434nm

chevy 383 4bolt 0.30 overbore.zero deck (compressie 10.5:1)
trw -34cc flat 2 reliefs
afr "190" 2.02/1.60 68cc
comp cam 292h 244/244@0.50 lift 501/501
mallory ignition (total timing ?)
weiand xcelerator single plane
holley 750 double pumper
th400 shiftkit en 2800 stall converter


whats wrong whit this combo
give me you idea's please thanks

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Old 08-13-2006, 07:36 AM
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My guess is something is seriously wrong with the dyno.

Vince
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Old 08-13-2006, 09:48 AM
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i think the compression would be 8.2:1 rather then 10.5:1
so he has to change te pistons with that hugh cam and 190cc ports


thanks
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Old 08-13-2006, 11:49 AM
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By -34cc I'm assuming you really mean 34cc dished? Otherwise you'd be look at something like 19:1 static C/R with domes at zero deck height. If 34cc dished is what you have than you'd be looking at around 8.1:1 static C/R with zero deck height and a .040 head gasket. And with that camshaft your dynamic C/R would be extremely low, so those dyno results seem to be about accurate.

I'd imagine it would be noticeable as that cam and c/r would be hard to get the engine to idle at a reasonable RPM with hardly any vacuum.
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Old 08-13-2006, 12:12 PM
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What's the application of the motor; street/strip, nitrous, forced induction, N/A, race fuel?

Last edited by Drewnashty; 08-13-2006 at 12:18 PM.
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Old 08-13-2006, 12:38 PM
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its a street motor
i asked him to get the piston part numbers so we
could get
a better idea
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Old 08-13-2006, 01:06 PM
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If he is shooting for 10.5:1 then with zero deck height, .040 gasket a set of pistons with a 6cc dish would put him at 10.51
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Old 08-13-2006, 04:01 PM
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I had a friend that had a very similar problem, and we still are not sure why it happend, Here is his motor:

383
pro topline 200cc heads
comp hyd flat tappet cam 236 242 @ .050 .530 lift
9.6:1
performer RPM air gap intake
holley 750 carb
comp pro magnum roller rockers

His motor only made 260 hp on an chassis dyno, and what is really weird is that it maxed out at 4200 RPM and then just flatlined. It really didnt drop off in power, it just stayed there. His transmission is slipping alot between gears, but I dont know if slipping while in gear could cause this type of problem. It seems to me that if his tranny was slipping that it could cause this to happen, but I am not sure. How is your tranny? Even with both motors running properly, yours should be making 50-75 hp more than his pretty easily if you were at 10.5:1. Based on a crate motor like his, it should be around 425 hp, which assuming a 22% loss to the rear wheels, would put it around 330 at the wheels, so he is way off where I think he should be. Your motor should be closer to around 475 hp pretty easily if it had 10.5:1 compression which would put you at around 370 at the wheels assuming the same loss. With 8.3:1, I would still think you should be putting out around 300 at the wheels though.

Adam
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Old 08-16-2006, 02:14 PM
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littel update pistons are 3.4 not 34cc

trw -l2491f30+ 383 10.76 64.0cc -3.4cc,flat
2 reliefs
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Old 08-16-2006, 02:47 PM
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I would check to make sure that the cam is degreed properly, that the lash is set to where it should be, and that he has good cylinder pressure.

Adam
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